1 The N-acetylation of dapsone (DDS) was studied in 160 unrelated healthy Jordanian volunteers. 2 The frequency of slow acetylators determined using the plasma monoacetyldapsone (MADDS) to DDS ratio (MADDS/DDS), was 67.5% with a 95% confidence interval of 59 to 76%. Slow acetylators had an acetylation ratio of < 0.42. 3 Applying the Hardy-Weinberg Law, the frequency of the recessive allele controlling slow acetylation was found to be 0.82 ± 0.02. 4 The frequency distribution histogram of the plasma MADDS/DDS ratio showed an apparent trimodal pattern. The number of homozygous (n = 16) and heterozygous (n = 36) rapid acetylators derived from the observed data did not agree with those predicted for the respective rapid acetylators (n = 5 and n = 47) according to the Hardy-Weinberg Law. The suggested antimode used to discriminate the two groups was 0.82. 5 The mean plasma concentration of MADDS and the mean plasma acetylation ratio were about three times lower in slow than in rapid acetylators. However, there was no difference in mean plasma DDS concentration between slow and rapid acetylators. 6 There was a significant correlation (r = 0.853, P < 0.001) between plasma MADDS concentration and the acetylation ratio. For DDS such a correlation was absent (r = 0.059, P = 0.23).

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The ability to oxidise trimethylamine (TMA) to trimethylamine N-oxide (TMAO) is distributed polymorphically within a British white population with the majority of individuals excreting greater than 90% of total urinary TMA as TMAO. The opposite extreme is characterised by a rare inborn error of TMA N-oxidation known as the fish-odour syndrome. However there is a lack of information regarding inter-individual variability in the N-oxidation of TMA in other ethnic groups. In this study the urinary excretion of TMA and TMAO was determined over a period of 24 h in 82 Jordanian subjects. A frequency distribution histogram of % of total urinary TMA excreted as TMAO revealed that the majority of subjects excreted greater than 80% of the total urinary TMA as TMAO, however eight subjects (9.7%) excreted less than 80% of the total TMA as TMAO. In a previous study of 169 white British subjects only one (0.6%) excreted less than 80% of the total TMA as TMAO. The results suggest that the prevalence of compromised ability to N-oxidise TMA may be higher in a Jordanian population than in a British population.

A rapid, specific and a one-stage protein precipitation method for simultaneous estimation of dapsone (DD S) and monoacetyldapsone (MAD) concentration in plasma and urine using high performance liquid chromatography (HPLC) is described. T h e applicability of the method for monitoring D D S and MAD blood levels in two different acetylator phenotype volunteers following the administration of 100-mg oral dose of D D S was shown. Cumulative urinary excretion of D D S and MAD were studied in the same volunteers.Correspondence: D r M. Abuirjeie,